Transversely sliding breech bolt lock for automatic firearms



C. E. SIMPSON Dec. 4, 1951 TRANsvERsELY sLTDTNG BREECH BOLT Locx FOR AUTOMATIC FIREARMS Filed om.l 29, 1948 3 Sheets-Sheet 1 ltLrEl-LUEA E -5iI ILj:1.5nTL @wwwa/TM c. E. SIMPSON 2,576,973 TRANSVERSELY SLIDING BREECH BOLT LOCK FOR AUTOMTIC FIREARMS Dec. 4, i951 Filed Oct. 29, 1948 mm MW M5 -m4 W 5 E. E E 1,. m )h Wh Dec. 4, 1951 c. E. SIMPSON 2,576,973

TRANSVERSELY SLIDING BREECH BOLT LOCK FOR AUTOMATIC FIREARMS Filed Oct. 29, 1948 3 Sheets-Sheet 3 [211179911129 E .AIILF .5011.

Patented Dec. 4, 1951 TRANSVERSELY SLEDING BREECH EOLT LOCK FOR AUTOlVSATIC FIREARMS Application October 29,1948, Serial No. 57,283

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 2 Claims.

The invention described in the specification and claims may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to a gas operated firearm of the automatic type employing a reciprocating bolt having a comparatively short recoil travel.

Numerous prior art firearms of relatively large caliber employ a long bolt travel and frequently use what is known as a U-feed for extracting the cartridge from the nrearm belt and seating such cartridge in the chamber of the barrel. For firearmsof relatively low rate of re, in the neighborhood of 60G-800 rounds per minute, such a feed is entirely satisfactory because of the relatively long time interval available for the bolt to complete its cycle of feeding and extraction of a cartridge,

vIt is also common with rearms oi this type to employ a breech block or bolt having considerable mass. Obviously to increase the speed of firearms having such a large reciprocating bolt mass, such bolt will have to be moved even faster with the unfortunate result that the reaction forces set up will be so great as to cause considerable breakage of the parts and will therefore require considerable redesign of aected components ci the firearm.

` In order to obtain a high rate of fire, it is there` fore ncessary to provide a reciprocating breech member having a very light mass. In addition, a bolt travel of a length not much greaterthan the length of the cartridge is necessary in order to get the rapidity of nre desired as such shortened bolt travel substantially reduces the time element.

Accordingly it is an object of this invention to provide a rearm having a reciprocating breech member of comparatively light weight wherein a high rate of nre may be obtained.

Another object of this invention is to provide a positive bolt locking device for an automatic firearm wherein locking is accomplished by extreme short movement of the breech lock actuator which is positive in operation and one which will adequately withstand a high breech pressure.

Still another object of this invention is to provide lan automatic irearm having a cartridge feeding mechanism operable by the operating slide of the rearm.

Another object of this invention is to provide 2 a latching device for insuring that the firearm bolt will precede the operating slide of the firearm into battery position in properly spaced relationship with respect to the operating member.

Still another object of this invention is to pro vide a cartridge support in the feedway of the firearm to support a cartridge being fed into the chamber while permitting the ejected empty cartridge case to drop through the receiver on the recoil stroke of the rearm.

The specific nature of the invention as well as other objects and advantages thereQf will clearly appear from the following description of a preierred embodiment as shown in the accompanying drawings in which:

Fig. l is a longitudinal sectional view of the rear portion of the firearm shown with the bolt in the breeched locked battery position.

Fig. 2 is a longitudinal sectional View of the front portion of the firearm with the mechanism in the breached locked battery position.

Fig. 3 is an enlarged detail fragmentary View showing the position of the cartridge support rods engaging the cartridge in such fashion that the bolt may readily seat the cartridge in the chamber of the firearm.

Fig. 4 is a view similar to Fig. 3 but showing the cartridge support rods in another position to permit ejection of the empty cartridge case.

Fig. 5 is a detail view showing the manner of mounting the extractor in the firearm bolt.

Fig. 6 is a perspective view of the extractor.

Fig. 7 is a view similar to Fig. 1 but showing the bolt in the extreme recoil position with a cartridge in position for feeding into the chamber of a firearm barrel.

Fig. 8 is a view similar to Fig. 2 but showing the mechanism in the extreme recoiled position.

Fig. 9 is a detail view showing the cam slots in the cartridge support rods whereby such rods are rotated to permit feeding of a cartridge or ejection of an empty case.

Fig. 10 is a detail view showing the bolt lock in locked relationship with the bolt and the relationship of thecam in the operating slide with respect to the bearing pins the bolt lool: where such bolt lock is in the loclged position.' l

Fig. 1l is a cross-sectional view taken along `the line .ll-H-H of Fie. l0 ,showing the bolt .100k in locked relationship with the firearm bolt.

Fig. 12 is a top schematic view of the lever arrangement utilized for transversely feeding a belt of cartridges through the feedway of the firearm and also showing the cam slot in the operating slide in the firearm for actuation of such levers.

Fig. 13 is an enlarged detail view showing the elements of the cartridge feeding mechanism in elevation.

Fig. 14 is a top. View of the receiver.

Fig. 15 is a longitudinal sectional view of the operating slide.

Fig. 16 is a top view of the operating slide.

Fig. 17 is a left end view of the firearm receiver shown in Fig. 1.

Fig. 18 is a top view showing the locking arrangement for the receiver and receiver extension.

The firearm shown in Fig. 1 comprises essentially a receiver 20, a barrel 33 secured to the forward end of receiver 2|) by threads 3|, a bolt 4D slidably mounted in receiver 2D and an oper.. ating slide 50 slidably mounted in receiver 20 below bolt 4G but connected thereto as will be later described.

Receiver 2l] comprises a substantially rectangular block as shown in Fig. 14. A cylindrical boss 2| is integrally provided on the forward end of such receiver and is exteriorly threaded as shown at 22 on which is screwed a barrel jacket 23. Boss 2| is provided with an axial hole 24 and such hole is threaded to receive threaded end 3| of barrel 30. A cover 25 is pivotally mounted on top of receiver 2|) by a pin 26. Such cover is releasably secured to receiver 26 by a latch 21 provided at the forward end of cover 25. Opposed integral depending lugs 28 are provided onthe underside of cover 25 which supporta cartridge belt feed slide 29. A belt feed slide lever 32 is pivotally secured to the underside of cover 25 by a pin portion 33 and functions in a manner as will be later described.

Suitable rectangular ways 34 and 35, as shown in Fig. 11, are provided in receiver 20 and are longitudinally disposed therein to receive respectively operating slide 50 and bolt 40. A receiver extension 36 is secured to the rear end of receiver 20 by an interlocking lug arrangement 31 and rivets or screws 38, as shown in Fig. 18. Receiver extension 36 supports a buffer housing 39 which contains any conventional energy absorbing means. A buffer plate 4| extends forwardly out of buier housing 39 against which operating slide U strikes, as will be later described.

Bolt 40 comprises a cylindrical body portion 42 terminating in a depending rectangular base portion 43 which slidably engages the ways 35 in receiver 2D. An axial hole 44 is provided in the cylindrical portion 42 of bolt 40 to receive a ring pin 45. A substantially vertically disposed recess 46 is provided in the bottom of rectangular portion 43 of bolt 40 for a purpose to be later described. A vertical slot 41 communicates recess 46 with hole 44 and permits a tang 48 provided on the rear of ring pin 45 to project downwardly into recess 46. The forward face of bolt 40 is provided with a cylindrical recess 49 coaxial with hole 44 to receive the head of a cartridge 5|, as shown in Fig. 1.

A locking shoulder 52 is provided on bolt 40 near the forward end thereof as shown in Fig. 5 and is produced by a substantially semiannular groove provided about the periphery of the cylindrical portion 42 of bolt 4|). Such groove, however, is eccentrically formed with respect to the axis thereof so that such groove terminates at approximately the sides of the circular portion of the bolt. The forward face of shoulder 52 is sloped to facilitate unlocking of a breech lock 54, as will be later described.

On the underside of bolt 40 on the forward cylindrical portion thereof, there is provided a slot 53 as shown in Fig. 5. Such slot is longitudinally disposed with respect to the axis of cylindrical portion 42 of bolt 43 and is of suitable Width to accommodate an extractor 55. A rectangular recess 55 is provided above and communicating with slot 53 to receive a transverse lug 51 provided on extractor 55. A transverse hole 58 is provided in bolt 40 which intersects recess 56. A pin 60 is insertable in hole 58 and is engageable with a hook portion 59 provided on lug 51 of extractor 55. Such pin thereby pivotally secures extractor 55 within slot 53. A cylindrical recess 6| is provided near the rear end of slot 53 and a corresponding cylindrical recess 62 is provided near the end of extractor 55 to accommodate a spring 63 which is provided to bias the forward end of extractor 55 into engagement with the rim. of cartridge 5|.

Bolt 40 is reciprocated on ways 35 Within receiver 20 by operating slide 50 which is slidably mounted on Ways 34 in receiver 20. Operating slide 5U is essentially a rectangular bar and a vertically disposed integral lug 64 is provided at the rear end of su-ch slide as shown in Figs. 15 and 16. Lug 64 rests within recess 46 thereby cooperating with bolt 40 to effect movement of such bolt when the slide is actuated, as Will be later described. A transverse slot 65 is provided on top of lug 54 to receive tang 48 of firing pin 45. Thus operating slide 50 acts as a hammer to actuate ring pin 45 t0 discharge cartridge 5| and also retracts firing pin 45 affording a safety feature, in a manner to be subsequently described.

A longitudinal slot 66 is provide-d in the center of operating slide 56 as shown in Fig. 16 in order that such slide can surround a bolt lock 54 and to permit assembly of such bolt lock as will be described in greater detail later.

Bolt lock 54 is a substantially rectangular member provided approximately in the center thereof with a hole 51, as shown in Fig. 11, which surrounds the cylindrical portion of bolt 40. Bolt lock 54 is provided with a depending integrally formed lug 68 which is of substantially inverted T-shape construction. The stem of such lug is provided with a longitudinal rectangulary recess 69 for a purpose to be later described. Near the bottom of lug 53 there is provided a transverse hole 10, shown in Fig. 10, and a corresponding hole 1| is provided at the juncture of the stem portion of lug 68 and the rectangular portion of lock 54. On the opposite sides of lug 58 there are provided sloped surfaces 12 as shown in Fig. 10 which support a pin 13 inserted through hole 10. A corresponding pin 14 is inserted through the hole 1| for a purpose which will presently appear. The forward face of lock 54 is beveled adjacent hole 61 to cooperate with the sloped locking shoulder 52 provided on bolt 40 whereby the lock cooperates to securely lock bolt 43 to' the firearm in a manner to be later described.

To permit the depending lug 68 of lock 54 to be assembled to operating slide 53, a pair of opposed Vertically disposed slots 15 are provided near the forward end of slot 55 in slide 50 shown in Fig. 16. Near the rear of slide 50 on the top surface thereof, as shown in Figs. 15 and 16, there is provided a pair of oppositely disposed mounted in a'vertically disposed hole ||3 provided in receiver 20 adjacent one end of slot 80 therein. A similar hole ||4 is provided on the opposite side of slot 80 whereby such shaft may be mounted on the opposite side of the receiver as will be later described. A lever II5 provided with a rounded end I I6is secured to the lever end of shaft I I2 and the rounded end I I6 thereof engages a cam groove I I8 longitudinally disposed on the side of operating slide 50. Groove II8 is so shaped that as the slide moves in its longitudinal path, the lever II5 being in contact with such groove, will eiect rotation of shaft II2, in turn rotating lever IIO, thence lever |08, thereby effecting pivotal movement of lever 32 which in turn translates such action to transverse movement of slide 29 with respect to the longitudinal axis of the rearm, thus a belt of cartridges may be fed through a feedway V|02 of the firearm as operating slide 50 reciprocates Within the receiver. By mounting shaft I|2 in the opposed vertically disposed hole I I4 in receiver 20 and by suitably remounting or reversing lever 32, the rearm can be readily converted to feeding from the side opposite to the one above described. A cam groove |20 identical to groove I|8 and opposed thereto is provided in operating slide 50 to effect rotational movement of shaft I|2 when feeding from the opposite direction.

Any suitable re control mechanism may be utilized with this firearm to retain the bolt and operating slide in the recoil position and to effect release thereof when and as desired. A sear I I9 is shown in Fig. '7 for retaining bolt 40 in operating slide 50 in the recoil position. Such sear is not shown connected to a fire control mechanism as any such mechanism may be utilized to eifect release thereof.

Operation In the breeched battery position of the breech elements of the firearm, as shown in Fig. l, bolt lock 54 is in locked relationship with bolt 40, hence the bolt is securely locked to the receiver. In such gure the operating slide 50 is shown in its extreme forward position wherein such slide has carried the firing pin 45 forwardly to discharge cartridge 5I. Upon discharge thereof a portion of the bullet propulsion gases escape through gas port 86 into gas cylinder 83 whereupon such gases impinge on the face of piston 85 thus forcing the operating rod 'I9 rearwardly against the bias of operating spring 88, operating rod 'I9 being connected to slide 50 forces such slide rearwardly.

As slide 50 moves to the rear approximately cam grooves 'I6 force pin 'I4 of lock 54 upwardly thereby raising lock 54 out of engagement with bolt 40 whereupon lug 64 of slide 50 contacts and forces bolt 40 rearwardly to the recoil position against buffer plate 4|. Driving spring B8 then returns operating slide 50 forwardly carrying bolt 40 along with such slide.

Shoulder 99 of latch 94 engages lug |00 of bolt 40 to maintain bolt 40 ahead of slide 50 or in spaced relationship with such slide in order that bolt 40 can readily pick up cartridge 5I in feedway |02, lever 32 in the meantime has been pivoted by shaft I I2 to move slide 29 across the feed- Way to position the cartridge directly in front of bolt 40 so that such bolt can advance a cartridge into the chamber of firearm barrel 30. g

During the counter-recoil movement of the bolt 40 in slide 50, cartridge support rods |03 have been rotated to the position shown in Fig.

4 whereby the flattened portion |01 thereof is vertically disposed so that the empty cartridge case extracted by extractor 55l from barrel 30 can be ejected downwardly through receiver 20. After the bolt has traveled approximately its recoil travel, rods I03 are rotated to the cartridge supporting position shown in Fig. 3 as governed by cam slots |05. As the bolt proceeds into battery position, rods |03 are again rotated by pins |06 being in engagement with cam grooves |05 to the position as shown in Fig. 4. As a cartridge is about to be seated in the chamber of the barrel, latch 94 enters slot 69 of breech lock 54 whereby latch 94 is unlocked from bolt 40 allowing such bolt to move into the locked battery position shown in Fig. l. When the bolt is in battery position, operating slide 50 proceeds forwardly approximately 1/2 to lock the bolt whereupon slide 50 continues forwardly approximately an additional 1A to drive firing pin 45 against the primer of a cartridge 5I seated in the chamber thereby effecting discharge of such cartridge whereupon the cycle of operation just described is repeated over again.

From the foregoing description it is apparent to those skilled in the art that a firearm of the automatic type having a bolt of comparatively light weight is hereby provided which will readily attain a high rate of re as the reciprocating members which include the bolt and operating slide have relatively light Weight as compared to prior art firearms, hence enabling such elements to be rapidly moved. The rearm herein disclosed is positively and securely locked at the moment of discharge of each cartridge thereby insuring a safe rearm at all times. The cartridge feeding means is positively assured by the cam action of the slide eifecting rotation of the belt feed lever thus insuring that timing thereof will be maintained at all times. The feature of supporting the round in the feedway as such round is being chambered is unique as such cartridge support will permit ejection of the empty cartridge through the receiver on the recoil` stroke of the firearm.

I claim:

1. In a rearm having a receiver, a bolt slidably mounted in the receiver for longitudinal reciprocating movement between a battery position and a recoil position, said bolt having a semiannular groove on the upper part thereof, an operating slide connected to said bolt, said slide being mounted in the receiver for reciprocal movement, a bolt lock slidably mounted in the receiver and adapted to surround said bolt in the battery position thereof, and means for engaging or disengaging said lock with said semi-annular groove in timed relationship with respect to the relative position of said slide whereby said bolt is locked or unlocked relative to the receiver.

2. In a firearm having a receiver, a bolt slidably mounted in the receiver for reciprocal movement between a locked breeched position and a recoil position, said bolt having a cylindrical head provided with an annular locking groove thereon, an operating slide connected to said bolt and mounted in the receiver for reciprocal movement, a bolt lock slidably mounted in the receiver for vertical movement, said bolt lock having a hole therethrough arranged to receive the cylindrical head of said bolt in the battery position thereof, cam means on said operating slide, and means on said bolt lock engageable with said cam means on said operating slide whereby said bolt lock is moved into or'outof 9 engagement with said locking groove in timed re- UNITED STATES PATENTS lationship With respect to the relative position Number Name Date. of said slide for locking or unlocking said bolt 1,290,851 Sturgeon Jam- 7, 1919 relative 130 the receiver. 1293,396 FOX Feb 4, 1919 CLARENCE E SIMPSON 5 1,323,356 Ballard Jan. 2o, 1920 1,340,891 Graham May 25, 1920 1,340,943 Eickhoi et a1. May 25, 1920 REFERENCES CITED 1,907,163 White May 2, 1933 The following references are of record in the 2,345,736 Eiane Apr. 4, 1944 le of this patent: 1o 2,373,794 swebilius Apr. 17, 1945 

